Process of treating fibrous material



Feb. 19, 1935. OLSSQN 1,991,413

PROCESS OF TREATING FIBROUS MATERIAL Filed May 2, 1933 I la INVENTOR Ell's Olssan BYE i v ATTORNEYS I Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to the treatment or digestion of fibrous material by chemical processes, such as the soda sulphate or sulphite processes.

More specifically stated, the invention relates 5 to the concentration and reclaiming of the treating liquor after the fibrous material has been treated therewith.

The invention has for its salient object to provide a process of the character described so carried out as to render the process efiicient and economical.

Another and more specific object of the invention is to provide a process of the character described so worked out as to utilize heatwhich 15 is wasted in the usual process of chemically treating fibrous material.

Another object of the invention is to provide a process of the character described for chemically treating fibrous material and for reclaim- !0 ing and concentrating the treating liquor so worked out that the heat in the liquor discharged from the digester can be utilized to concentrate the used liquor.

Further objects of the invention will appear 25 from the following specification taken in connection with the drawing which forms apart of this application, and in which Fig. 1 illustrates diagrammatically an arrangement of apparatus for carrying out the process;

30 and Fig. 2 shows a modified embodiment of the invention using a second evaporator.

The invention briefly described consists of a process for chemically digesting fibrous material if) and reclaiming the digesting liquor, including the use oi steam,,from a separator which receives the digested material from the digester and also the treating liquor, for raising the temperature of the used liquor. The used liquor at the raised l0 temperature is passed from the heater to apparatus for concentrating the liquor.

Although the process is not limited to any particular form or type of apparatus the drawing illustrates diagrammatically one set of apparatus which is adapted for carrying out the process. In the drawing there is shown a digester D which is supplied with a charge of fibrous material and with suitable chemical digesting liquor. The material is cooked in the liquor and when the digestion has been completed the fibrous material and treating liquor are withdrawn from the digester through a pipe and are conducted to a suitable separator S known in the trade as a cyclone tank". From the separator S the liquor and fibrous material are passed through a The fibrous material is removed from the dif- 5 fusers through doors 13 and the used liquor which has been diluted by the addition of the water is discharged from the bottom of the difiuser and conducted through a pipe 14 to a liquor storage tank T.

The steam from the hot liquor in the separator S is conducted from the top of the separator through a pipe to a heater H. The liquor is pumped from the tank T by a pump P through a pipe 21 to the heater H and passes from the heater, at a raised temperature through a pipe 22 to a concentrating or flash tank J. This device is provided with a plurality of baflles 23 which breakup the hot liquor and the volatile portions thereof are removed from the top of the tank through a pipe 24 which is connected to a suitable vacuum device such as barometric jet condenser B. The concentrated liquor is removed from the bottom of the tank J through a pipe 25 and is conducted thereby to the storage tank T. The volatile portions of the liquor pass through the jet condenser and through a pipe 26 into a receptacle R, being discharged under water.

The concentrated liquor is discharged or removed from the tank T through an outlet pipe 2'1 and passes to evaporators.

It should be understood that the process is not limited to the use of one or any particular number of evaporators or evaporating steps and Fig. 2 shows a further evaporator interposed between the flash tank J and the barometric jet condenser B.

In Fig. 2 there is shown an evaporator E having a steam belt or coil C which receives steam from the flash tank J through the pipe 24' which corresponds to pipe 24 shown in Fig. 1. By steam belt is meant the section of the evaporator receiving the steam which may pass through coils surrounded by liquor or the liquor may pass through the coils and be surrounded by steam.

The liquor is conducted to the evaporator E through a pipe 30 and is heated by the steam coil or steam belt C. The steam from the liquor passes from the evaporator E through an outlet 31 to a vertical pipe 32 and thence through a pipe 33 to a barometric condenser B similar to the condenser B shown in Fig. 1. The concentrated liquor from the evaporator E is discharged through the pipe 34 and the steam condensate is discharged through the pipe 35.

With the apparatus shown in Fig. 2 the evaporator is preferably under a vacuum of approximately twenty-four to twenty-six inches and the flash tank is under a lower vacuum of approximately ten to fifteen inches. By this arrangement the efliciency is increased over the efliciency obtained by the constructions shown in Fig. 1.

From the above description it will be seen that the steam from the hotliquor is utilized to raise the temperature of the diluted liquor which is withdrawn from the diifuser or diil'users into astorage tank and is conducted from the tank through a heater which is heated by the steam separated from the liquor in the separator S. This effects a very material saving in heat and the temperature of the liquoris materially raised in the heater or-condenser H, as for instance,

tials, or from the spirit and scope of the invention, as set forth in the appended claims.

What I claim is: g

1. The process of chemica1lydigesting fibrous material and reclaiming and concentrating the treating liquor, which consists of;d igesting the material with hot liquor, separatingfst'eam from the hot liquor and treated material when the digester is discharged, washing the fibrous material, collecting the liquor from" thewasher, continuously heating the collected liquor by heat derived from the separated steam, and concentrating the heated liquor by removing the more volatile portions thereof.

2. The process of chemically digesting fibrous material and reclaiming and concentrating the treating liquor, which consists of digesting the material with hot liquor, separating steam from the hot liquor and treated material when the digester is discharged, washing the fibrous material, collecting the liquor from the washer, continuously heating the collected liquor by heat derived from the separated steam, concentrating the heated liquor by removing the more volatile portions thereof, and further concentrating the liquor by heat derived from the said volatile portions.

3. In combination, a digester for fibrous material, a separator connected to the digester for receiving the digested material therefrom, a diffuser for receiving and washing the material from the separator, a storage receptacle, means for conducting liquor from the diffuser to the storage receptacle, a heater for heating the liqnor from the storage receptacle, means for continuously conducting liquor from the storage receptacle through said heater, means for conducting steam from the separator to the heater to heat the liquor, means for receiving and concentrating the heated liquor from the heater, and meansfor conducting the concentrated liquor back to the storage receptacle.

4. In combination, a digester for fibrous material, a separator connected to the digester for receiving the digested material from the digester and separating steam from the liquor, washing apparatus for washing the material, a storage receptacle receiving the liquor from the washing apparatus, a heater for raising the temperature of the liquor from the washing apparatus, means for conducting the steam from the separator to the heater, means for separating steam from the heated liquor anad concentrating the liquor, an evaporator, and means for heating the evaporator by steam derived from the said steam separating and concentrating means.

ELIS OLSSON. 

